Several new developments have occurred in mass spectrometry instrumentation which offer significant improvements for applications in biomedical research. A number of biomedical researchers at the University of California, Davis, in the Colleges of Argicultural and Environmental Sciences, and Letters and Science, and in the Schools of Medicine and Veterinary Medicine have needs for mass spectrometric capability which exceeds in sophistication the equipment now on campus and in availability that located elsewhere in Northern California. Taking these factors into account, this proposal is for purchase and installation of a mass spectrometer with high resolution, high mass range, multiple ionization, GC interface, and data system to serve as the primary instrument for shared use by 15 faculty investigators engaged in biomedical research at Davis. The instrument will be located in an established campuswide large instrument facility (Facility for Advanced Instrumentation), and will be operated and maintained under direct supervision of the facility staff. A plan for administration of the mass spectrometer, including University cost sharing in its purchase (co-equal with the amount requested from NIH), and University subsidy in its operation and maintenance, has been established with provisions for continued administration through an advisory committee reporting directly to the Dean of Research.